The invention relates to improvements in filters, and more particularly to a filter for cleaning raw gases wherein the filter medium consists of a bulk layer of material preferably one that is resistant to high temperatures.
In gas cleaning filters of the type heretofore known, the filter medium commonly consisted of a single coherent bulk material layer horizontally located in a filter housing. A raw gas stream was conducted through the bulk material layer downwardly and the waste substances present in the gas which commonly consisted of solids, were absorbed and collected by the bulk layer material. The gas thus cleaned of the substances was then discharged through a clean gas channel.
Since the absorption capacity of the bulk material layer is relatively limited for agents precipitated out of the raw gases, the bulk material layer must be cleaned or freed of the deposited substances at regular intervals. When the bulk material layer had to be cleaned, the raw gas stream had to be interrupted and shut off while scavenging air was conducted through the bulk material layer and until the collected substances were removed. This structure and operation was disadvantageous in that it did not enable a continuous operation for cleaning gases. Thus, in order to obtain a continuous cleaning, it was necessary to provide two filters structured in such a manner as to be disposed in parallel and operating alternately so that they could be alternately subjected to a cleaning of the bulk material layer. This made such arrangements relatively involved and increased the cost of construction and the cost of operating.
It is accordingly an object of the present invention to provide an improved bulk material filter which avoids the foregoing disadvantages and which is capable of continuous operation with a cleaning of the filter material with a requirement of reduced space and reduced construction costs.
A further object of the invention is to provide a filter structure which enables improved filtering of raw gases with the use of bulk filter material utilizing a structure and operation which provides for maximum gas flow through without interruption due to cleaning of the filter material. A further object of the invention is to provide an improved filter structure which has accommodations for improved cleaning of the bulk filter material and which provides means for supplying fresh filter material without interrupting the continued filtering operation.
A feature of the invention accomplishing the above objectives embodies a filter which is divided into a plurality of chambers each containing a bulk material filling means with the chambers being annularly disposed around a central waste channel for the withdrawal of substances removed from the gases. The chambers are connected to each other via openings in the wall of the centrally located waste channel. Each chamber is connected to a raw gas feed from above and a clean gas discharge conduit leads from the lower end of each chamber. A plurality of annularly arranged intermittently operated chambers are thus provided so that continued filtering operation can be continued while one or more chambers is being subjected to a reverse flow of gas for a cleaning operation.
In accordance with the improved structure, each chamber is provided with a feeder for the admission of a filter medium which is located above the layer of bulk material, and means are provided for used filter medium to be removed without interrupting continual filtering operation and allowing for fresh filter material to be injected into the chamber.
In accordance with a feature of the invention, the layer of material in each of the chambers is disposed in a frusto-conical shape so as to resemble a funnel. This provides for a significant increase in the filter surface area as contrasted with a filter of the type heretofore available wherein the material was simply horizontally disposed in the filter. With the present arrangement, an overall filter housing of a given dimension is capable of providing substantially increased filtering area. This provides for improved cleaning, but is well adapted for refilling of the bulk material layer and for cleaning the bulk material layer.
In accordance with the invention, jets are provided for the feed of cleaning agents with the jets located in the outer chamber walls below the surface of the bulk material. With the use of these jets, the upper layer of the bulk material is blown off along with the substances which have been filtered out of the raw gas stream each time a cleaning occurs. By removal of the upper layer, an entire replacement of bulk material is not necessary, but the bulk material can be replenished and cleaned periodically and frequently in a manner which does not interrupt the continual operation of the filter.
A further cleaning of the filter material is accomplished in that each of the chambers has a clean discharge conduit leading downwardly from it, and each conduit is provided with at least one injector which is capable of introducing a cleaning gas or agent beneath the bed of the bulk filter material in each of the chambers. Thus, a cleaning of the bulk material layer can be accomplished from below as well as from the side. By the cleaning agent introduced below the bed, a pressure can be supplied opposing the weight of the layer of bulk material and opposing the flow of incoming raw gases. With the application of fresh gas from below, an agitation or cleaning of the bulk layer is accomplished augmented by a cleaning off of the top layer with the jets disposed in the filter chamber walls.
Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims, and drawings in which: